1. Field of the Invention
The present invention relates to a heating apparatus and a heating method, which are for heating a substrate on which a film is coated, and a computer readable storage medium storing a computer program for causing the heating apparatus to perform the heating method.
2. Description of the Related Art
A coater/developer for coating an organic material film such as a resist film or the like on a substrate and developing the film is provided with a heating apparatus for heating and/or cooling the substrate.
As an example of such a heating apparatus, a substrate heating apparatus 101 is described in reference to FIG. 1. In the substrate heating apparatus 101, a substrate 103 is placed on a heating plate 102 and heated by a heater 104 embedded in the heating plate 102. During heating the substrate 103, nitrogen is supplied toward the substrate 103 so as to purge volatile substances such as organic solvents from the organic film. While the nitrogen or the like is exhausted by an exhaust apparatus 110, the volatile substances are collected by a collection portion 105. In such a substrate heating apparatus 101, when the back surface of the substrate 103 directly contacts the top surface of the heating plate 102, particles may be attached on the back surface of the substrate 103. In order to avoid the particles being attached on the back surface, the heating plate 102 is provided with plural pins 108 and the substrate 103 is placed on the plural pins 108. In this configuration, the substrate 103 is heated through an air layer, which is generally referred to as a proximity gap, formed between the back surface of the substrate 103 and the top surface of the heating plate 102.
By the way, when a film, for example, a resist film is formed on the substrate 103, the stress between the film and the substrate 103 may warp the substrate 103. In order to uniformly heat the substrate 103 even in this situation, there is known a thermal processing technique in which the heating plate 102 is provided with plural suction conduits 106 through which the substrate 103 is attracted onto the heating plate 102 by a vacuum pump 107, which is often referred to as a vacuum chuck method, thereby maintaining the substrate 103 flat with respect to the heating plate 102. As stated above, since the atmosphere in the substrate heating apparatus 101 is contaminated with, for example, volatile substances and/or sublimated substances from the resist film or the like, when the substrate 103 is attracted through the suction conduits 106, such substances are evacuated into the suction conduits 106. The substances flowing through the suction conduits 106 when cooled are condensed on the inside walls of the suction conduits 106, thereby narrowing the inner diameters of the suction conduits 106, which impairs the suction performance. As a result, the substrate 103 may no longer be attracted and thus uniform thermal processing is impaired.
In addition, Patent Document 1 listed below discloses a technique that can substantially confine the air layer between the substrate and the heating plate so as to prevent air from flowing therebetween. However, this technique cannot be employed when the edge area of a back surface of the substrate is contaminated by a resist solution since the contaminated edge area contacts a top surface of the heat plate so as to produce particles from the resist.
Patent Document 1: Japanese Laid-Open Patent Publication No. H06-338450 (paragraph 0027)
The present invention has been made in view of the above and is directed to a technique that can prevent a suction force from being reduced by condensation/precipitation of volatile substances and/or sublimated substances onto the inside walls of suction conduits through which suction force the substrate is attracted onto the heating plate by suction, thereby improving in-substrate temperature uniformity and substrate-to-substrate temperature uniformity.